A compressed-air feed system is used in vehicles of all types, in particular for feeding compressed air to an air suspension system of a vehicle. Air suspension systems may also comprise ride-height control devices with which the distance between a vehicle axle and vehicle body can be adjusted. An air suspension system of a pneumatic system mentioned in the introduction comprises a number of air bellows which are pneumatically connected to a common line (gallery) which, with increasing filling, can raise the vehicle body and, with decreasing filling, can correspondingly lower said vehicle body. With increasing distance between the vehicle axle and vehicle body, or ground clearance, the spring travels become longer, and it is also possible for greater ground unevennesses to be travelled over without contact with the vehicle body occurring. Such systems are preferably used in off-road vehicles and sport utility vehicles (SUVs). In the case of SUVs in particular, in the case of very high-powered engines, it is desirable for the vehicle to be equipped, on the one hand, with a relatively small ground clearance for high speeds on roads, and to be equipped, on the other hand, with a relatively large ground clearance for off-road travel. It is furthermore desirable for a change in the ground clearance to be implemented as quickly as possible, which increases the demands with regard to speed, flexibility and reliability of a compressed-air feed system.
DE 102 23 405 B4 describes an air suspension system for a motor vehicle, having a compressor, having a dryer connected downstream of the compressor, having ride-height control valves by means of which individual air springs assigned to the vehicle wheels can be actuated, having a pressure line which connects the compressor to the air springs, having a ventilation line, having a section of the pressure line between dryer and ride-height control valves, in which section a throttle is arranged parallel to a check valve, and having a switching valve, which is arranged parallel to the pressure line section, such that the throttle has a variable flow cross section. By means of this variable flow cross section, which operates as a throttle, and an electromagnetic switching valve, the outflow speed of the air mass that is discharged via the ride-height control valves in the event of a lowering of the vehicle ride height can be adjusted.